Inohara H, Raz A
Michigan Cancer Foundation, Department of Pathology and Radiation Oncology, Wayne State University, School of Medicine, Detroit 48201, USA.
Cancer Res. 1995 Aug 1;55(15):3267-71.
Galectin-3 (Gal-3) is a beta-galactoside-binding protein with M(r) approximately 30,000. Cell surface Gal-3 is postulated to be involved in homotypic aggregation of tumor cells in the circulation during metastasis through attachment to a complementary serum glycoprotein(s), which serves as a cross-linking bridge between adjacent cells. To test this hypothesis a recombinant strain of baculovirus encoding Gal-3 was used to infect Sf9 insect cells, which lack endogenous Gal-3. Immunoblotting and indirect immunofluorescence studies revealed that the infection with recombinant virus conferred Gal-3 expression on Sf9 cells, and the Gal-3 was localized on the cell surface as well as in the cytoplasm. Sf9 cells infected with recombinant virus underwent homotypic aggregation in the presence of exogenous glycoprotein (i.e., asialofetuin), whereas control cells uninfected or infected with wild-type virus did not. Lactose and Fab' fragments of anti-Gal-3 antibodies markedly inhibited the cell-cell aggregation. Moreover, cosuspension of Sf9 cells infected with the recombinant virus with uninfected cells in the presence of asialofetuin resulted in a preferential cell-cell adhesion of the Gal-3-expressing cells. These results directly demonstrate the ability of cell surface Gal-3 molecules to mediate homotypic cell adhesion by bridging through branched, soluble complementary glycoconjugates.
半乳糖凝集素-3（Gal-3）是一种分子量约为30,000的β-半乳糖苷结合蛋白。据推测，细胞表面的Gal-3在转移过程中通过与一种互补血清糖蛋白结合参与循环中肿瘤细胞的同型聚集，该血清糖蛋白充当相邻细胞之间的交联桥。为了验证这一假设，使用编码Gal-3的重组杆状病毒株感染缺乏内源性Gal-3的Sf9昆虫细胞。免疫印迹和间接免疫荧光研究表明，重组病毒感染使Sf9细胞表达Gal-3，且Gal-3定位于细胞表面以及细胞质中。在存在外源性糖蛋白（即去唾液酸胎球蛋白）的情况下，感染重组病毒的Sf9细胞发生同型聚集，而未感染或感染野生型病毒的对照细胞则未发生。乳糖和抗Gal-3抗体的Fab'片段显著抑制细胞间聚集。此外，在存在去唾液酸胎球蛋白的情况下，将感染重组病毒的Sf9细胞与未感染细胞共悬浮，导致表达Gal-3的细胞优先发生细胞间黏附。这些结果直接证明了细胞表面Gal-3分子通过分支的可溶性互补糖缀合物桥接介导同型细胞黏附的能力。
